1. Field of the Invention
The present invention relates to a polypropylene resin composition. More particularly, the present invention relates to a polypropylene resin composition capable of forming shaped articles that are light, have excellent rigidity, are resistant to thermal deformation, have impact resistance and moldability and have an enhanced resistance to whitening due to stress applied thereto during a forming procedure. The polypropylene resin composition of the present invention is advantageously usable for interior parts of automobiles and, typically, the trim.
2. Description of the Related Art
It is known that polypropylene resin compositions comprising, as a principal component, a polypropylene resin, for example, a crystalline ethylene-propylene block copolymer, combined with an elastomer such as an ethylene-propylene copolymer rubber, ethylene-butene copolymer rubber or hydrogenation product of a styrene-butadiene block copolymer, and an inorganic filler such as talc, have excellent rigidity and impact strength and superior moldability, and thus have been widely employed for the production of parts of automobiles.
Also, studies have been conducted to enhance the rigidity, impact resistance and moldability of the polypropylene resin compositions by variously changing the polypropylene resin, the elastomer and the inorganic filler.
As an above-mentioned type of polypropylene resin composition, Japanese Unexamined Patent Publication (Kokai) No. 58-168649 discloses a combination of a crystalline ethylene-propylene block copolymer with a specific ethylene-.alpha.-olefin copolymer rubber and talc.
Also, a combination of a crystalline ethylene-propylene block copolymer with a specific hydrogenated styrene-butadiene block copolymer, ethylene-propylene copolymer rubber and talc has been discussed in Japanese Unexamined Patent Publication (Kokai) No. 3-172,339.
Further, a combination of a crystalline ethylene-propylene-block copolymer with a specific hydrogenated styrene-butadiene block copolymer, ethylene-butene copolymer rubber and talc has been discussed in Japanese Unexamined Patent Publication (Kokai) No. 4-57,848.
Although the above-mentioned conventional polypropylene resin compositions exhibit a high levels of rigidity and impact resistance, they are not yet satisfactory in lightness and exhibit an unsatisfactory resistance to whitening of the resultant shaped article.